Hi Monks, I can not figure out why the two programs below cause different responses from server.

The server returns a string (presenting an array) and then you can request and fetch deltas from your last request to get the array via a header.

Using LWP::UserAgent things work fine:

use strict;
use warnings;
use LWP::UserAgent;

my $ua = LWP::UserAgent->new(keep_alive => 1);
my $url = "http://example.com/myUrl";
my $token = undef;

while(1)
{
    my $res = $ua->get($url, 'Start-From' => $token // "", 'X-AcceptDe
+ltaUpdates' => 'true');
    $token = $res->headers->{'token'} if ($res->headers->{'token'});
    print $res->decoded_content if ($res->is_success);
    sleep 4;
}
[download]

Array is: ['item1','item2']
Add ['item3']
No update
Add ['item4']
No update
Add ['item5']
No update
...
[download]

However using HTTP::AnyEvent I get bizarre behaviour (this is a silly way to do timing I know but I am just keeping things as simple as possible for testing):

use strict;
use warnings;
use AnyEvent;
use AnyEvent::HTTP;
my $url = "http://example.com/myUrl";
my $token = undef;

while(1)
{
    my $cv = AnyEvent::condvar;
    my $instance = http_request GET => $url,
        headers => { 'Start-From' => $token // "", 'X-AcceptDeltaUpdat
+es' => 'true' },
        keepalive => 1,
        persistent => 1,
        sub {
            my ($data, $headers) = @_;
            $token = $headers->{'token'} if (defined $headers->{'token
+'});
            print $data if ($data);
            $cv->send;
        };
    $cv->recv;
    
    $cv = AnyEvent::condvar;
    my $timer = AnyEvent->timer(after=>4, interval => 4, cb => sub {
        $cv->send;
    });
    $cv->recv;
}
[download]

Array is: ['item1','item2']
No update
No update
No update
No update
No update
No update
Array is: ['item1','item2','item3','item4']
No update
No update
No update
No update
No update
No update
...
[download]

I have tried comparing the headers sent (by setting up a HTTPD server) and all the requests seem to be identical with headers sent. So I don't understand the difference. I am basically about to resort to using wireshark to see if I can determine what is different at a TCP/HTTP level. But is there anything obvious I am missing here?